How do I add a manifest to an executable using mt.exe?

I'm trying to use mt.exe from the Windows SDK to add a manifest to an executable file that doesn't have one, using the following command line:

C:\winsdk61>mt.exe -nologo -manifest "r:\shared\hl.exe.manifest" -updateresource:"r:\shared\hl33m.exe;#1"

Unfortunately, when I do, I get this error:

mt.exe : general error c101008c: Failed to read the manifest from
the resource of file "r:\shared\hl33m.exe". The specified resource
type cannot be found in the image file.

Of course the resource wasn't found in the file - the file doesn't have a manifest, that's why I want to add one.

How can I append a manifest to an executable file? Shouldn't this be simple?